Reliability block diagrams to model disease management

Background and objectives. Studies of diagnostic or therapeutic procedures in the management of any given disease tend to focus on one particular aspe ct of the disease and ignore the interaction between the multitude of facto rs that determine its final outcome. The present article introduces a mathe matical model that accounts far the joint contribution of Various medical a nd non-medical components to the overall disease outcome. Methods. A reliab ility block diagram is used to model patient compliance, endoscopic screeni ng, and surgical therapy for dysplasia in Barrett's esophagus. Results. The overall probability of a patient with a Barrett's esophagus to comply with a screening program, be correctly diagnosed with dysplasia, and undergo su ccessful therapy is 37%. The reduction in the overall success rate, despite the fact that the majority of components are assumed to function with reli ability rates of 80% or more, is a reflection of the multitude of serial su bsystems involved in disease management. Each serial component influences t he overall success rate in a linear fashion. Building multiple parallel pat hways into the screening program raises its overall success rate to 91%. Pa rallel arrangements render systems less sensitive to diagnostic or therapeu tic failures. Conclusions. A reliability block diagram provides the means t o model the contributions of many heterogeneous factors to disease outcome. Since no medical system functions perfectly, redundancy provided by parall el subsystems assures a greater overall reliability.